An engine mount (antivibration device) according to the related art includes, for example, as described in Patent Document 1: a cylindrical outer cylinder (first mounting member) connected to a vibration-receiving section such as a vehicle body; an inner cylinder (second mounting member) connected to a vibration-generating section such as an engine; an elastic body which elastically connects the outer cylinder to the inner cylinder and blocks the opening end of one side of the outer cylinder; a diaphragm which blocks the opening end of the other side of the outer cylinder; and a partition plate which divides a liquid chamber that is formed between the elastic body and the diaphragm and has a liquid sealed therein, into a main liquid chamber that uses the elastic body as a portion of the wall surface thereof and a sub-liquid chamber that uses the diaphragm as a portion of the wall surface thereof. The partition plate and the diaphragm mentioned above are members which are made entirely of rubber. The partition plate is fitted to the inner side of the above-mentioned outer cylinder from the opening end of the lower side thereof, and the diaphragm is fitted to the inner side of the outer cylinder, at the rear of the partition plate. Thereafter, the outer cylinder is covered with a cup-shaped holder from the lower side, and the diaphragm is pressed from the lower side by the holder. As a result of the holder pressing the diaphragm from the lower side, the partition plate and the diaphragm are interposed between the elastic body and the holder in stacked state such that the above-mentioned engine mount is assembled. In the above-mentioned engine mount, since the partition plate is entirely formed of rubber, the generation of noise due to cavitation may be suppressed.